This invention relates generally to measuring liquid depth and particularly to measuring liquid level in containers located, both above and below ground.
U.S. Pat. No. 4,802,363, which issued Feb. 7, 1989 to one of the present inventors, discloses an apparatus for measuring liquid level, which although satisfactory for some uses, is inconvenient for some situations that arise in measuring liquid levels. The device disclosed in U.S. Pat. No. 4,802,363 has a rectangular float that is centered in a rectangular tube. Using this device requires rotation of a handle to unlock the float so that it can float to the liquid surface. The rectangular bar that actuates this locking action must be precisely centered along the full length of the rectangular tube in order to assure that a false lock will not occur. If this center rectangular bar becomes even slightly bent, twisted or concentrically displaced due to rough usage, it can cause the measuring float to be jammed in the tube and give an erroneous reading.